Whether they're training or taking part in actual competitions, athletes have to maintain a delicate balance – they want to make sure that they're "giving it everything they've got," yet they don't want to push themselves to the point that they cramp up or drop from exhaustion. That's why the BSXinsight was created. Billed as being the world's first wearable lactate threshold sensor, it's made to let athletes know how close they're getting to the edge, so they can approach it but not go over.

When we perform any sustained vigorous physical activity, lactate (the base of lactic acid) builds up in our bloodstream. Once those levels get too high, the body simply isn't able to produce the required energy anymore. That's the point at which we "hit the wall," and it's called the lactate threshold.

The usual method of checking lactate levels is via finger-prick blood tests – although a scientist at the University of California, San Diego is working on a temporary tattoo-type biosensor that does the job. The BSXinsight instead uses light, to provide real-time readings on a paired smartphone or smart watch.

The device consists of a stretchable cuff that's worn on the calf, and an electronic module that can be snapped in and out of a receptacle on the back of that cuff. The module contains an LED array and a light detector. That array emits light into the muscle tissue, some of which is reflected back to the detector. The manner in which that light is reflected is affected by metabolic activity within that tissue. Therefore, by analyzing that light, it's possible to determine the lactate level in that muscle.

Readings are sent via Bluetooth or ANT+ to the user's mobile device. It, in turn, lets them know if they should ease up, or if they can in fact push themselves even harder. The BSXinsight additionally keeps track of parameters such as calories burned and cadence, to further help users track their performance.

BSX Athletics, the Houson-based designer of the BSXinsight, ran a successful Kickstarter campaign earlier this year. The first commercially-produced units should begin shipping next month, and can be preordered for US$420. Buyers can choose between Cycling, Running and Multisport models.